feat(wasm): execute client handlers without requests

req: client_local/001\nreq: client_local/004\nreq: client_local/005\nreq: client_local/009\nreq: client_local/010\nreq: client_local/014\nreq: v1_release/001

hemx-derive/src/lib.rs

@@ -10,7 +10,20 @@ use syn::{
 };
 
 #[proc_macro_attribute]
-pub fn handler(_attr: TokenStream, item: TokenStream) -> TokenStream {
+pub fn handler(attr: TokenStream, item: TokenStream) -> TokenStream {
+    let placement = attr.to_string();
+    let is_client = match placement.as_str() {
+        "" => false,
+        "client" => true,
+        _ => {
+            return syn::Error::new(
+                proc_macro2::Span::call_site(),
+                "unsupported hemx handler placement; expected #[hemx::handler] or #[hemx::handler(client)]",
+            )
+            .into_compile_error()
+            .into();
+        }
+    };
     let function = parse_macro_input!(item as ItemFn);
     let name = function.sig.ident.to_string();
 
@@ -73,7 +86,45 @@ pub fn handler(_attr: TokenStream, item: TokenStream) -> TokenStream {
         .into();
     }
 
-    quote!(#function).into()
+    if !is_client {
+        return quote!(#function).into();
+    }
+    if !function.sig.inputs.is_empty()
+        || function.sig.asyncness.is_some()
+        || function.sig.unsafety.is_some()
+        || function.sig.constness.is_some()
+        || !function.sig.generics.params.is_empty()
+    {
+        let message = format!(
+            "client-local hemx handler `{name}` must be a safe, synchronous, non-generic function with no parameters"
+        );
+        return quote!(
+            #function
+            compile_error!(#message);
+        )
+        .into();
+    }
+
+    let function_name = &function.sig.ident;
+    let export_name = format_ident!("__hemx_client_{function_name}");
+    let export_module = format_ident!("__hemx_client_export_{function_name}");
+    quote!(
+        #function
+
+        #[cfg(target_arch = "wasm32")]
+        mod #export_module {
+            use ::hemx::wasm as wasm_bindgen;
+
+            #[::hemx::wasm::wasm_bindgen(js_name = #export_name)]
+            pub fn invoke() -> ::std::vec::Vec<u8> {
+                ::hemx::wasm::encode_handler_effect(
+                    super::#function_name(),
+                    crate::ui::BUILD_FINGERPRINT,
+                )
+            }
+        }
+    )
+    .into()
 }
 
 #[proc_macro_attribute]